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Version 1.0 – January 2010

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Datasheet SHT21

Humidity and Temperature Sensor

 Fully calibrated

 Low power consumption

 Excellent long term stability

 DFN type package – reflow solderable

Dimensions

Figure 1:

Drawing of SHT21 sensor package, dimensions are

given in mm (1mm = 0.039inch), tolerances are ±0.1mm. Die

pad (centre pad) is internally connected to VSS. NC are floating.

VSS = GND, SDA = DATA.

Sensor Chip

SHT21 features a generation 4C CMOSens® chip.

Besides the capacitive relative humidity sensor and the

band gap temperature sensor, the chip contains an

amplifier, A/D converter, OTP memory and a digital

processing unit.

Material Contents

While the sensor itself is made of Silicon the sensors’

housing consists of a plated Cu lead-frame and green

epoxy-based mold compound. The device is fully RoHS

and WEEE compliant, e.g. free of Pb, Cd and Hg.

Additional Information and Evaluation Kits

Additional information such as Application Notes is

For more information please contact Sensirion via

For SHT21 two Evaluation Kits are available: EK-H4, a

four-channel device with viewer software, that also serves

for data-logging, and a simple EK-H5 directly connecting

one sensor via USB port to a computer.

1.0

1.0

2.4

0.3

0.4

1.1

SCL

SDA

NC

NC

VSS

VDD

Bottom View

3.0

2.2

0.8 typ

0.3 typ

Product Summary

SHT21, the new humidity and temperature sensor of

Sensirion is about to set new standards in terms of size

and intelligence: Embedded in a reflow solderable Dual

Flat No leads (DFN) package of 3 x 3mm foot print and

1.1mm height it provides calibrated, linearized signals in

With a completely new designed CMOSens® chip, a

reworked capacitive type humidity sensor and an

improved band gap temperature sensor the performance

has been lifted even beyond the outstanding level of the

previous sensor generation (SHT1x and SHT7x). For

example, measures have been taken to stabilize the

behavior at high humidity levels.

Every sensor is individually calibrated and tested. Lot

identification is printed on the sensor and an electronic

identification code is stored on the chip – which can be

read out by command. Furthermore, the resolution of

SHT21 can be changed by command (8/12bit up to

12/14bit for RH/T), low battery can be detected and a

checksum helps to improve communication reliability.

With made improvements and the miniaturization of the

sensor the performance-to-price ratio has been improved

– and eventually, any device should benefit from the

cutting edge energy saving operation mode. For testing

SHT21 a new evaluation Kit EK-H4 is available.